Pressure advance calculator: tower height or test line to the value to save

The formula

Every pressure advance test steps the value up from a start value by a fixed amount. The calculator counts the steps up to the height or line you picked.

Klipper TUNING_TOWER with FACTOR, and with BAND added:

pressure advance = START + FACTOR × height
pressure advance = START + FACTOR × (floor(height / BAND) + 0.5) × BAND

OrcaSlicer and Bambu Studio PA Tower:

pressure advance = start + step × whole millimeters of height

Line and pattern tests (OrcaSlicer and Bambu Studio PA Line and PA Pattern, Marlin’s K-factor pattern):

pressure advance = start + (line number − 1) × step

• Height is in millimeters, measured from the bed.
• START, FACTOR and BAND are the numbers in your TUNING_TOWER command.
• Start, end and step are the numbers the slicer or generator asked for.
• Line number counts the line or pattern labeled with the start value as 1.
• PA Tower, PA Line and PA Pattern are the slicers’ names for their pressure advance (PA) tests.

How do you calculate pressure advance from a tower test?

Add the start value to the factor times the height you measured from the bed. On a Klipper tuning tower that is START + FACTOR × height, so a long-bowden tower at FACTOR=.020 read at 12.90 mm gives 0 + 12.90 × 0.020 = 0.258. OrcaSlicer’s PA Tower changes once per millimeter, so drop the decimals.

Worked example: Klipper tuning tower

These are the calculator’s defaults, and the example in Klipper’s own docs.

1. The tower was printed after TUNING_TOWER COMMAND=SET_PRESSURE_ADVANCE PARAMETER=ADVANCE START=0 FACTOR=.020, Klipper’s command for long bowden extruders.
2. Calipers read 12.90 mm from the bed to the height picked.
3. Pressure advance: 0 + 12.90 × 0.020 = 0.258.
4. Run SET_PRESSURE_ADVANCE ADVANCE=0.258 to use it now. To keep it, set pressure_advance: 0.258 in the [extruder] section of printer.cfg and run RESTART, which also clears the test state.

The same 12.90 mm on the direct drive tower (FACTOR=.005) gives 0.0645.

Klipper pressure advance tuning tower settings

Klipper’s docs give START=0 FACTOR=.005 for direct drive and START=0 FACTOR=.020 for long bowden extruders. Klipper sets a new value on every layer, so the measured height goes straight into the formula. Its test object, square_tower.stl, is 50 mm tall. That puts the direct drive tower’s range at 0 to 0.25 and the bowden tower’s at 0 to 1.

Two optional parameters change the arithmetic:

• BAND: Klipper changes the value only every BAND millimeters and uses the figure for the middle of each band. At 12.90 mm with FACTOR=.005 BAND=5, the height falls in the 10 to 15 mm band: 0 + 0.005 × 12.5 = 0.0625.
• SKIP: Klipper holds START up to the SKIP height and counts up from that point. Subtract SKIP from the measured height first. With SKIP=2, 12.90 mm on the bowden tower gives 0 + 10.90 × 0.020 = 0.218.

Pressure advance tower in OrcaSlicer

OrcaSlicer’s PA Tower and Bambu Studio’s PA Tower for third-party printers set a new value once per whole millimeter. The first millimeter above the bed prints the start value. A reading of 8 mm or 8.4 mm falls in the 8 to 9 mm band: 0 + 8 × 0.002 = 0.016. OrcaSlicer’s wiki writes this as start + step × measured height.

OrcaSlicer’s dialog fills in defaults for a DDE (direct drive extruder) or a Bowden setup. It cuts the tower to (end − start) / step + 1 mm, so its top millimeter prints the end value. Both default ranges give a 51 mm tower.

Tower test	Settings	Range covered	Height read	Value
Klipper, direct drive	START=0 FACTOR=.005	0 to 0.25 over 50 mm	10 mm	0.05
Klipper, direct drive	START=0 FACTOR=.005	0 to 0.25 over 50 mm	25 mm	0.125
Klipper, long bowden	START=0 FACTOR=.020	0 to 1 over 50 mm	12.9 mm	0.258
Klipper, long bowden	START=0 FACTOR=.020	0 to 1 over 50 mm	20 mm	0.4
OrcaSlicer PA Tower, DDE	0 to 0.1, step 0.002	51 mm tower	8 mm	0.016
OrcaSlicer PA Tower, DDE	0 to 0.1, step 0.002	51 mm tower	23.6 mm	0.046
OrcaSlicer PA Tower, Bowden	0 to 1, step 0.02	51 mm tower	8 mm	0.16
OrcaSlicer PA Tower, Bowden	0 to 1, step 0.02	51 mm tower	23.6 mm	0.46

How to measure the height

1. Measure with calipers from the bottom of the tower, where it sat on the bed, to the height you picked.
2. For Klipper, type the reading as it is, because the value changed on every layer.
3. For OrcaSlicer, type the reading too. The calculator drops the decimals and shows the unrounded figure in its note.

How do you calculate pressure advance from a line or pattern test?

Start from the test’s start value and add one step for each line after the first: start + (line number − 1) × step. The line labeled with the start value is line 1. On OrcaSlicer’s default PA Line test, which starts at 0 in steps of 0.002, line 9 is 0 + 8 × 0.002 = 0.016.

Worked example: OrcaSlicer PA Line

1. Test settings: OrcaSlicer’s PA Line for a direct drive extruder, start 0, end 0.1, step 0.002. That prints 51 lines.
2. The line picked is the 9th, counting the line labeled 0 as line 1.
3. Pressure advance: 0 + (9 − 1) × 0.002 = 0.016.
4. In OrcaSlicer’s filament settings, tick Enable pressure advance and type 0.016 under Pressure advance. Save the filament preset.

Labels sit on every other line

OrcaSlicer and Bambu Studio print the value beside every other line or pattern, starting with the first. Marlin’s generator labels “every second test line” the same way. So labels sit beside 1, 3, 5 and so on.

An unlabeled line is one step above the label before it. On the default PA Line, line 10 has no label. Line 9’s label reads 0.016, so line 10 is 0.018.

Line or pattern test	Settings	Printed	No. 5	No. 10	Last
OrcaSlicer PA Line, DDE	0 to 0.1, step 0.002	51	0.008	0.018	0.1
OrcaSlicer PA Line, Bowden	0 to 1, step 0.02	51	0.08	0.18	1
OrcaSlicer PA Pattern, DDE	0 to 0.08, step 0.005	17	0.02	0.045	0.08
OrcaSlicer PA Pattern, Bowden	0 to 1, step 0.05	21	0.2	0.45	1
Bambu Studio manual Flow Dynamics, Bambu Lab printer	0 to 0.05, step 0.005	11	0.02	0.045	0.05
Marlin K-factor pattern	0 to 2, step 0.2	11	0.8	1.8	2

Bambu Studio’s dialog for third-party printers fills in the same defaults as OrcaSlicer.

Both slicers print (end − start) / step + 1 lines or patterns, rounded up. A shallow bed gets fewer PA Line lines: OrcaSlicer spaces them 3.5 mm apart and fits at most (bed depth − 10) / 3.5. A 180 mm deep bed holds 48 lines, not 51.

Where to save the value

The value goes in the firmware’s config or the slicer’s filament settings, and the calculator prints the line for the one you pick. The table uses 0.258.

Firmware or slicer	Set it now	Keep it
Klipper	SET_PRESSURE_ADVANCE ADVANCE=0.258	pressure_advance: 0.258 under [extruder] in printer.cfg, then RESTART
Marlin	M900 K0.258	M500 saves it to EEPROM, or add M900 K0.258 to the end of the slicer’s start G-code
RepRapFirmware	M572 D0 S0.258	The same line in config.g. D0 is the first extruder.
OrcaSlicer	Filament settings → Filament → Flow ratio and Pressure Advance: tick Enable pressure advance, type 0.258	Save the filament preset
Bambu Studio, third-party printer	Filament settings → Filament → Basic information: tick Enable pressure advance, type 0.258	Save the filament preset
Bambu Studio, Bambu Lab printer	Calibration → Flow Dynamics: type 0.258 as Factor K on the Record Factor step	Bambu Studio saves it to the printer

In OrcaSlicer and Bambu Studio, the Pressure advance field shows only in Advanced mode. Bambu Studio hides it altogether on Bambu Lab printers.

Marlin’s M900 needs firmware built with LIN_ADVANCE. OrcaSlicer’s wiki notes that not every printer ships with it enabled.

When the result is out of range

• Below zero. Klipper rejects a negative pressure advance. Marlin’s M900 accepts K from 0 to 10. OrcaSlicer writes no pressure advance command for a negative value. A negative result means the start value or the step was typed wrong.
• Above the tower or past the last line. The test never printed that value. Check the height or the line count, and check that start, end and step match the test you printed.
• Above 2. OrcaSlicer and Bambu Studio accept at most 2 in the filament settings, and Bambu Studio’s Factor K must be above 0 and below 2.
• Exactly 0. Klipper’s default of 0 turns pressure advance off, and M900 K0 turns off Linear Advance in Marlin.